Apparatus For Melting And Refining Silica-Based Glass

ABSTRACT

An apparatus for melting and refining a silica-based glass composition includes a vertical first reaction chamber having an input adjacent to a lower end for receiving glass-forming components. The glass-forming components are heated to elevated temperature during upward flow through the vertical first reaction chamber to form a glass precursor melt adjacent to an upper end of the vertical first reaction chamber. A vertical second reaction chamber has an input adjacent to an upper end and an output adjacent to a lower end for delivering glass melt. A cross passage connects the upper end of the vertical first reaction chamber to the upper end of the vertical second reaction chamber such that the precursor melt flows from the vertical first reaction chamber through the cross passage and then through the vertical second reaction chamber to homogenize the precursor melt. Vacuum preferably is applied to the cross passage both to assist upward flow through the vertical first reaction chamber, and to assist refining of the precursor melt during such upward flow and during flow through the cross passage.

The present disclosure relates to an apparatus for melting and refining silica-based glass, and particularly to such an apparatus that employs a sodium-calcium-silicate glass as an intermediate precursor product.

BACKGROUND AND SUMMARY OF THE DISCLOSURE

Silica-based glass, such as soda-lime glass, is prevalent in the manufacture of glass containers and other products. Formation of a raw glass melt typically involves mixing various glass-forming components at elevated temperature. The glass typically has a residence time in a furnace on the order of twenty-four hours to dissolve the solids and refine the glass by driving off gases. The gases must be driven off ultimately to produce a solidified glass product without entrained bubbles. (The process of removing bubbles and bubble-forming gasses in molten glass is called “refining.”) In addition to being undesirably slow, this in-furnace process involves a large amount of space and high-energy input.

The general object of the present disclosure is to provide an apparatus for making silica-based glass, which is compact and modular. Another object of the disclosure is to provide an apparatus for making a silica-based glass melt, which can readily be scaled up or down as needed to provide a desired glass output.

The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.

Apparatus for melting and refining a silica-based glass composition, in accordance with one aspect of the present disclosure, includes a first melting vessel for receiving and melting silica-based glass forming components, a first vertical chamber having an inlet adjacent to a lower and operatively coupled to said first melting vessel to receive melted glass-forming components from said first melting vessel, a second vertical chamber spaced from and separate from the first vertical chamber, and a cross passage connecting an upper end of the first vertical chamber to an upper end of the second vertical chamber. Glass melt from the first melting vessel flows upward through the first vertical chamber, through the cross passage and then downward through the second vertical chamber to refine and homogenize the glass melt from the first melting vessel. A vacuum preferably is applied to the cross passage to assist upward flow of the glass melt through the first vertical chamber.

The cross passage preferably receives cullet to mix with the glass melt prior to and during flow through the second vertical chamber. The cross passage can have an input for receiving additional materials such as silica and minor ingredients or additives so that such additional materials are mixed with the glass melt during flow through the cross passage and the second vertical chamber. As an alternative, a second melting vessel can be operatively disposed between the first melting vessel and the first vertical chamber for adding additional materials such as silica and minor additives to the glass melt prior to passage through the first vertical chamber. In such modification, vacuum can be applied to the first and/or second melting vessel at least partially to refine the glass melt prior to passage through the first vertical chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objects, features, advantages and aspects thereof, will best be understood from the following description, the appended claims and the accompanying drawings, in which:

FIG. 1 is a block diagram of an exemplary process for reacting, melting and refining silica-based glass in an apparatus of the present disclosure;

FIG. 2 is a schematic diagram of an apparatus for reacting, melting and refining a silica-based glass composition in accordance with an exemplary embodiment of the present disclosure;

FIG. 3 is a schematic diagram that illustrates a number of the modular apparatus in FIG. 2 disposed in parallel for selectively increasing glass output;

FIG. 4 is a block diagram of a second exemplary process for reacting, melting and refining silica-based glass in an apparatus of the present disclosure; and

FIG. 5 is a schematic diagram of an apparatus for reacting, melting and refining a silica-based glass composition in accordance with the process of FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Co-pending patent application Ser. No. 13/288,681 filed Nov. 3, 2011 (Docket 19128) discloses a process for melting and refining silica-based glass, which can be implemented employing an apparatus of the present disclosure. In general, the co-pending application discloses a process for making a glass precursor melt, which includes mixing at least one glass network former with at least one glass network modifier, and refining the glass precursor melt by performing at least part of the mixing step at elevated temperature under reduced pressure to promote release of gases produced by the precursor melt. Additional glass network formers but, preferably, no additional glass network modifiers are mixed with the precursor melt to form a glass product melt. Cullet and/or minor additives such as colorants can be added. The disclosure of such co-pending application is incorporated herein by reference.

FIG. 1 illustrates a process for making silica-based glass in accordance with one exemplary embodiment in such co-pending application, which process is implemented in the exemplary apparatus of FIG. 2 of the present application. A first stage 20 of the process in FIG. 1 involves melting, reacting and refining input materials, preferably under vacuum (reduced pressure) and production of a low-viscosity sodium-calcium-silicate solution in liquid phase by melting, reacting and refining substantially all of the desired network modifiers and silica. This reaction produces an at least partially refined silicate precursor glass melt in liquid phase. The silicate solution precursor melt or intermediate product of first stage 20 is fed to a second stage 30, which involves mixing, dissolution and homogenization of the glass precursor melt with additional raw materials 40 including any shortfall of glass network formers such as silica and/or minor additives such as colorants. Stage 30 preferably also receives cullet (recycled glass) 50, and produces a soda-lime glass melt.

FIG. 2 illustrates an apparatus 60 for implementing the process of FIG. 1 (or more generally the process of the above-referenced co-pending application). Apparatus 60 includes a vertical first reaction chamber 62 having an input adjacent to a lower end 63 for receiving glass-forming components, such as from an induction-heated crucible 64. Vertical first reaction chamber 62 has an upper end 65 coupled to a cross passage 66 having an interior coupled to a vacuum pump or the like 68 for reducing pressure in cross passage 66. Cross passage 66 also has an input 70 for receiving additional raw materials such as silica and minor additives in stage 40 of FIG. 1. A vertical second reaction chamber 72 has an input 73 adjacent to an upper end coupled to cross passage 66 and an output 75 adjacent a lower end for delivering glass melt. At least vertical first reaction chamber 62, and preferably also cross passage 66, has heating elements 74 coupled to a suitable temperature control 76 for controlling the temperature within the reaction chamber and cross passage.

Application of vacuum to cross passage 66, by means of vacuum pump 68 for example, not only assists upward flow of glass-forming materials through vertical first reaction chamber 62, but also assists refining (removal of air bubbles) of the precursor melt in cross passage 66 during such upward flow and during flow through the cross passage to vertical second reaction chamber 72. The low viscosity of the glass material flowing through vertical first reaction chamber 62 not only assists such upward flow under vacuum but also promotes release of gas bubbles.

Vertical second reaction chamber 72 preferably includes at least one cross wall 80, and preferably a plurality of cross walls 80, effectively dividing the vertical second reaction chamber into a plurality of mixing cells 82. Cross walls 80 help prevent direct passage of unmelted solids through the vertical second reaction chamber. The upper cells 82 promote final dissolution of any unmelted solids in the glass stream flowing through reaction chamber 72, while the lower cells promote cooling of the glass stream to a desired output glass delivery temperature. A shaft 84 preferably extends through at least some of the cells 82 and paddles 86 preferably are coupled to shaft 84 in at least some of the cells. Shaft 84 is coupled to a motor 88 or the like for rotating the shaft and the paddles further to promote mixing and homogenization of the glass melt during downward flow through vertical second reaction chamber 72 toward glass delivery output 75. One or more cells 82 can include heaters 74 coupled to control 76, and the temperatures within the various cells 82 of vertical second reaction chamber 72 preferably are controlled so that glass is delivered at output 75 at a temperature suitable for use immediately to form glass gobs in a glassware-forming machine, for example.

In the preferred embodiment illustrated in FIG. 2, a vertical third reaction chamber 92 has an input 93 adjacent to a lower end for receiving cullet, such as in an induction-heated crucible 94. Heaters 74 are coupled to a temperature control 76 for controlling the temperature of cullet glass flowing upward through vertical third reaction chamber 92. The upper end 95 of vertical third reaction chamber 92 is connected to cross passage 66 so that cullet flowing into cross passage 66 is mixed with the precursor glass melt prior to and during downward flow through vertical second reaction chamber 72. Reduced pressure (“vacuum”) in cross passage 66 assists upward flow of cullet and refining (as needed) of the cullet during such upward flow. It is estimated that the process of FIG. 1 can be completed in the apparatus of FIG. 2 in six hours (as compared with twenty-four hours typical in current furnaces). This would involve about two hours of upward flow in chamber 62 and four hours of downward flow in chamber 72.

FIG. 3 illustrates parallel connection of several apparatus 60, which can be selectively enabled or disenabled to control the volume of glass flow through a glass output channel 96 or the like.

FIG. 4 illustrates a process as a modification to the process of FIG. 1 in accordance with a second exemplary embodiment of the present disclosure. The precursor melt output of first stage 20 is fed as an input to stage 40 in this embodiment, in which any shortfall in silica is added to the precursor output of stage 20, along with any desired minor additives such as colorants. The output of stage 40 is then fed as an input to mixing, dissolution and homogenization stage 30, from which a soda-lime glass melt emerges. Cullet, if desired, is fed as an input to stage 30.

FIG. 5 illustrates an apparatus 100 for implementing the process of FIG. 4 in accordance with an exemplary embodiment of the present disclosure. A vessel 110 such as an induction-heated crucible receives the calcium carbonate, sodium carbonate and silica inputs of stage 20 in FIG. 4 and forms a precursor melt. Vacuum 112 preferably is applied to vessel 110 at least partially to refine the precursor glass melt. By way of example only, the temperature within vessel 110 can be in the range of 1280° C. to 1300° C. A dam 114 can be employed to control glass flow and prevent the migration of un-melted glass forming materials into the second melting vessel 116.

The precursor glass melt output of vessel 110 is fed through a passage 118 to a second melting vessel 116. Process stage 40 in FIG. 4 takes place in vessel 116, in which the shortfall of silica is added to the precursor glass from vessel 110, along with any minor additives such as colorants. A paddle 120 or the like is coupled to a motor 122 for stirring the blend in vessel 116 to promote mixing and release of gas. Vessel 116 is coupled to a vacuum source 124 for assisting in the removal of any gases released within vessel 116.

The molten glass from vessel 116 is drawn through first vertical chamber 62 to cross passage 66 and thence to second vertical chamber 72. In this embodiment, cullet preferably is added to a reaction vessel 126 coupled to cross passage 66. A dam 128 prevents migration of un-melted cullet to chamber 66. Thus, precursor melt from vessel 110, silica and any minor additives added in vessel 116 and cullet optionally added in vessel 126 flow together through second vertical chamber 72. As in the embodiment of FIG. 2, motor 88 is coupled by a shaft 84 to various paddles or the like to mix and blend the glass constituents flowing though chamber 72 prior to emergence as delivered glass.

There thus has been disclosed an apparatus for making silica-based glass that fully satisfies all of the objects and aims previously set forth. The disclosure has been presented in conjunction with presently preferred embodiments, and alternatives and modifications have been discussed. Other alternatives and modifications readily will suggest themselves to persons of ordinary skill in the art in view of the foregoing description. The disclosure is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims. 

1. Apparatus for melting and refining a silica-based glass composition, which includes: a first melting vessel for receiving and melting silica-based glass forming components, a first vertical chamber having an inlet adjacent to a lower end operatively coupled to said first melting vessel to receive melted glass-forming components from said first melting vessel, a second vertical chamber spaced from and separate from said first vertical chamber, and a cross passage connecting an upper end of said first vertical chamber to an upper end of said second vertical chamber, such that glass melt from said first melting vessel flows upward through said first vertical chamber, through said cross passage and then downward through said second vertical chamber to refine and homogenize the glass melt from said first melting vessel.
 2. The apparatus set forth in claim 1 including means for applying a vacuum to said cross passage to assist upward flow of the glass melt through said first vertical chamber.
 3. The apparatus set forth in claim 2 including a shaft extending through at least a portion of said second vertical chamber, paddles coupled to said shaft, and means coupled to said shaft for rotating said shaft and said paddles to stir the glass melt during passage through said second vertical chamber.
 4. The apparatus set forth in claim 2 wherein said cross passage includes means for receiving cullet to mix with the glass melt prior to and during flow through said second vertical chamber.
 5. The apparatus set forth in claim 2 wherein said cross passage has an input for receiving additional materials such as silica and minor additives so that such additional materials are mixed with the glass melt during flow through said cross passage and said second vertical chamber.
 6. The apparatus set forth in claim 2 including a second melting vessel operatively disposed between said first melting vessel and said first vertical chamber for adding additional materials such as silica and minor additives to the glass melt prior to passage through said first vertical chamber.
 7. The apparatus set forth in claim 6 including means for applying vacuum to said first melting vessel and/or said second melting vessel at least partially to refine the glass melt prior to passage through said first vertical chamber.
 8. Apparatus for melting and refining a silica-based glass composition, which includes: a vertical first reaction chamber having an input adjacent to a lower end for receiving glass-forming components, said glass-forming components being heated to elevated temperature during upward flow through said vertical first reaction chamber to form a glass precursor melt adjacent to an upper end of said vertical first reaction chamber, a vertical second reaction chamber having an input adjacent to an upper end and an output adjacent to a lower end for delivering glass melt, and a cross passage connecting said upper end of said vertical first reaction chamber to said upper end of said vertical second reaction chamber such that said glass precursor melt flows from said vertical first reaction chamber through said cross passage and then through said vertical second reaction chamber to homogenize the precursor melt.
 9. The apparatus set forth in claim 8 including means for applying a vacuum to said cross passage both to assist upward flow of said glass-forming components through said vertical first reaction chamber, and to assist refining of said precursor melt during such upward flow and during flow through said cross passage.
 10. The apparatus set forth in claim 9 wherein said cross passage has an input for receiving additional materials such as silica and minor additives so that said additional materials are mixed with said precursor melt during flow through said cross passage and said vertical second reaction chamber.
 11. The apparatus set forth in claim 9 wherein said vertical second reaction chamber includes at least one cross wall dividing said vertical second reaction chamber into a plurality of mixing cells to help prevent direct passage of unmelted solids through said vertical second reaction chamber.
 12. The apparatus set forth in claim 9 including a shaft extending through at least a portion of said vertical second reaction chamber, paddles coupled to said shaft, and means coupled to said shaft for rotating said shaft and said paddles to stir the glass melt during passage through said vertical second reaction chamber.
 13. The apparatus set forth in claim 9 including a vertical third reaction chamber having an input adjacent to a lower end for receiving cullet and an output adjacent to an upper end coupled to said cross passage for refining the cullet during upward flow through said vertical third reaction chamber and mixing the cullet with the precursor melt during downward flow through said vertical second reaction chamber.
 14. The apparatus set forth in claim 13 including temperature control means coupled to said vertical third reaction chamber for controlling temperature of cullet entering said cross passage.
 15. The apparatus set forth in claim 9 wherein said apparatus is a modular apparatus that is selectively connectable and disconnectable and parallel with other modular apparatus as set forth in claim 2 for selectively increasing and decreasing total glass melt output from said apparatus.
 16. The apparatus set forth in claim 9 including temperature control means coupled to said vertical first reaction chamber for controlling temperature of the precursor melt entering said cross passage. 